I think this is a Bitgo privatekey backup format. I've created already a bitcoin account with Bitcold i've got after backuping my key a similar file:
{"iv":"0fSuBvpAJG36OEGHC59VEg==","v":1,"iter":10000,"ks":256,"ts":64,"mode"
:"ccm","adata":"","cipher":"aes","salt":"hE44Rh**fBI=","ct":"XPU**7nMb/rW
4jDeUAstbutIJxKKleh3XZ+ThTMnIj52ilQYMza3D3DNS6YnngplUl3/**Bj
ipFmpQVqWUSnuQ2786ySCkaNw2wgjc7yRY7MonYdeDFtvNzTJX4GLpgS/Kg**="}
Bitgo proposes an ethereum wallet called www.ether.li (multisig wallet)
and they use the same previous format :
{"iv":"/TWPASFYuO**P5Q==", "v":1, "iter":1000, "ks":128, "ts":64, "mode":"ccm", "adata":"", "cipher":"aes", "salt":"Udg***Ckg=", "ct":"1MsES**vhp4X**FiFTyup2**8Fw1lsDA***pMigSo8/R**/iOaVdCYbjAaT04Y7****"}
in their Api there is a function to decrypt the key:
var encryptedString = '{"iv":"n4zHXVTi/Go/riCP8fNs/A==","v":1,"iter":10000,"ks":256,"ts":64,"mode":"ccm","adata":"","cipher":"aes","salt":"zvLyve+4AJU=","ct":"gNMqheicMoD8ZmNzRwuQfWGAh+HA933l"}';
var decryptedString = bitgo.decrypt({ password: "password", input: encryptedString });